In many machine installations, especially in installations wherein massive portions of the machines are fabricated machined separately such as in the case of hydraulic turbines, the stay ring is machined, drilled and tapped at one setup. At a later time the outer headcover is machined, spot faced and drilled to provide access openings for the insertion of bolts for joining the outer headcover to the stay ring. In these instances, it is not possible to line the outer headcover bolt hole with the tapped bolt opening in the stay ring. It is especially difficult to establish alignment between the bolt openings because they are located inside of the headcover where it is impossible for a drilling machine to have access and even with so-called portable drills there is no place to effect a clamping of the drilling machine. Thus, the drilled and tapped bolt hole in the stay ring must be formed separately from the bolt opening in the headcover. With this condition existing, it has been impossible to provide a complete flat mating engagement between the bearing face of the bolt head and a spot face on the headcover and provide a seal to prevent water leakage around the bolts and water would fill up the cavity in the headcover flooding the entire powerhouse chamber. Lead washers or similar deformable metallic material has been used below the bolt head but this has not proven successful since the lead washers flatten out on one side and split. Rubber has been tried but proven unsuccessful as it did not seal properly and would blow out through the opening.